OBSERVATIONS ON POLYZOA. 103 



The peculiar elevation of the arms, however, indicates the 

 presence of a muscle which can only be situated in the 

 plane of the lophophore and attached at its two extremities 

 respectively near the tips of the arms, and in the vicinity 

 of the oral aperture. Just before entering the coenoecial 

 cell they are thrown up posteriorly and after emerging 

 therefrom frequently sustain this position for a considerable 

 time, which would not be possible without the aid of 

 strong muscles situated in the ceilingd of the arms in a 

 position similar to that ascribed to the lophophoric 

 flexor. The great expansion of the bases of the flexors 

 around the mouth and the coarseness of the fibres, also 

 indicate a muscular rather than a nervous tissue. Finally 

 I have been able to trace a continuous filament for some 

 distance in the arms and on the outer borders of these 

 bands, from which alone arise the nervous filaments, 

 branching; ofl' to the bases of the tentacles. 



O 



Thus, although not so fortunate as to detect the inti- 

 mate structure of their tissues, or to see them in action, I 

 have but little doubt that the bands inclosed between the 

 branches of the lophophoric nerve-trunks are muscular 

 (PL 13, fig. 13, M). 



The outer Tentacular Bands line the sides of the ten- 

 tacles, two bands to every tentacle (PI. 11, fig. 1, PI. 12, 

 fig. 2, PL 13, fig. 15, PL 14, fig. 1 ? O) . Starting in pairs 

 from the sides of the brachial contractors below the bases 

 of the tentacles, they continue to within a short distance 

 of their ends, and there spread out in fan shaped attach- 

 ments. These attachments joining in each tentacle, when 

 contracted, form an annular constriction, which gives a pe- 

 culiar swollen, or club like aspect to the sensitive tips (PL 

 14, fig. 7). The fibres of the opposite bases on the sides 

 of the brachial contractors also intermingle, and the space* 

 between, not being obscured by the fibres of these bands 

 or the thickness of the contractors themselves, are much 

 thinner and comparatively clear. Besides these there are 

 inner Tentacular Bands consisting of numerous fibres de- 

 scending from the inner sides of the tentacles, and running 

 in parallel lines along the floor of the arms toward the per- 



